INTRODUCTORY ESSAY. 229
The chain of mountains which separates the waters of the
Brahmaputra from rthose of the Irawadi, branches off from
this main axis at an acute angle. Its direction is south-
west, and it decreases rapidly in elevation after leaving the
Mishmi countrjr, forming the Naga hills, which extend from
96J0 E. long, to the sources of the Cachar and Manipnr rivers,
and have an average height of 6000 or 7000 feet. Here the
chain bifurcates, one branch running due west as far as the
great bend of the Brahmaputra, while the other nnis nearly due
south. The western branch, under the name of the Caehar,
Jaintia, Khasia, and Garrow hills, separates the valley of As-
sam from that of Silhet. Its elevation varies from 4000 to
7000 feet. The other, which separates Cachar, Chittagong,
and Aracan, from Ava, has been called the Aeng range; it is
less known, but is in many parts probably equally elevated.
The provinces of Eastern India selected for botanical divi-
1. Mishmi. 6. Aracan.
2. Assam, 7- Ava and Pegu.
3. Naga and Khasia* 8. Tcnasscrim.
4. Cachaj and Silhet. 9. Malayan Peninsula.
5. Chittagong and Tippera.
The country between India and China to the cast of Assam
is as little known as any other on the globe. Between the -
British frontier and that of China there arc interposed a
number of savage tribes, constantly at war, and so extremely
jealous of one another that no offers of reward have been suc-
cessful in inducing them to. guide travellers into the interior
of their mountains, though many efforts have been made since
Assam was conquered by the Indian Government during the
first Burmese war. At that time (as we learn from Captain
Wilcox's very interesting narrative) a corps of scientific sur-
veyors was attached to the army in the field, in order to l>c